p_laplacian_fixed_point.cc

The p-Laplacian problem by the fixed-point method

#include "rheolef.h"
using namespace rheolef;
using namespace std;
#include "eta.h"
#include "dirichlet.icc"
int main(int argc, char**argv) {
environment rheolef (argc,argv);
geo omega (argv[1]);
Float eps = std::numeric_limits<Float>::epsilon();
string approx = (argc > 2) ? argv[2] : "P1";
Float p = (argc > 3) ? atof(argv[3]) : 1.5;
Float w = (argc > 4) ? (is_float(argv[4]) ? atof(argv[4]) :2/p) :1;
Float tol = (argc > 5) ? atof(argv[5]) : 1e5*eps;
size_t max_it = (argc > 6) ? atoi(argv[6]) : 500;
derr << "# P-Laplacian problem by fixed-point:" << endl
<< "# geo = " << omega.name() << endl
<< "# approx = " << approx << endl
<< "# p = " << p << endl
<< "# w = " << w << endl
<< "# tol = " << tol << endl;
space Xh (omega, approx);
Xh.block ("boundary");
trial u (Xh); test v (Xh);
form m = integrate (u*v);
problem pm (m);
field uh (Xh), uh_star (Xh, 0.);
uh["boundary"] = uh_star["boundary"] = 0;
field lh = integrate (v);
dirichlet (lh, uh);
derr << "# n r v" << endl;
Float r = 1, r0 = 1;
size_t n = 0;
do {
form a = integrate(compose(eta(p),norm2(grad(uh)))*dot(grad(u),grad(v)));
field mrh = a*uh - lh;
field rh (Xh, 0);
pm.solve (mrh, rh);
r = rh.max_abs();
if (n == 0) { r0 = r; }
Float v = (n == 0) ? 0 : log10(r0/r)/n;
derr << n << " " << r << " " << v << endl;
if (r <= tol || n++ >= max_it) break;
problem p (a);
p.solve (lh, uh_star);
uh = w*uh_star + (1-w)*uh;
} while (true);
dout << catchmark("p") << p << endl
<< catchmark("u") << uh;
return (r <= tol) ? 0 : 1;
}
lh
field lh(Float epsilon, Float t, const test &v)
Definition: burgers_diffusion_operators.icc:25
Float
see the Float page for the full documentation
field
see the field page for the full documentation
form
see the form page for the full documentation
geo
see the geo page for the full documentation
problem
see the problem page for the full documentation
rheolef::dout
odiststream dout(cout)
see the diststream page for the full documentation
Definition: diststream.h:430
rheolef::derr
odiststream derr(cerr)
see the diststream page for the full documentation
Definition: diststream.h:436
space
see the space page for the full documentation
test
see the test page for the full documentation
trial
see the test page for the full documentation
dirichlet.icc
The Poisson problem with homogeneous Dirichlet boundary condition – solver function.
dirichlet
void dirichlet(const field &lh, field &uh)
Definition: dirichlet.icc:25
eta.h
The p-Laplacian problem – the eta function.
mkgeo_ball.n
int n
Definition: mkgeo_ball.sh:150
mkgeo_sector.m
m
Definition: mkgeo_sector.sh:118
rheolef
This file is part of Rheolef.
Definition: compiler_eigen.h:37
rheolef::dot
rheolef::std enable_if ::type dot const Expr1 expr1, const Expr2 expr2 dot(const Expr1 &expr1, const Expr2 &expr2)
dot(x,y): see the expression page for the full documentation
Definition: vec_expr_v2.h:415
rheolef::grad
std::enable_if< details::is_field_convertible< Expr >::value,details::field_expr_v2_nonlinear_terminal_field< typename Expr::scalar_type,typename Expr::memory_type,details::differentiate_option::gradient >>::type grad(const Expr &expr)
grad(uh): see the expression page for the full documentation
Definition: field_expr_terminal.h:911
rheolef::integrate
std::enable_if< details::is_field_expr_v2_nonlinear_arg< Expr >::value &&! is_undeterminated< Result >::value, Result >::type integrate(const geo_basic< T, M > &omega, const Expr &expr, const integrate_option &iopt, Result dummy=Result())
see the integrate page for the full documentation
Definition: integrate.h:202
rheolef::norm2
T norm2(const vec< T, M > &x)
norm2(x): see the expression page for the full documentation
Definition: vec.h:379
rheolef::is_float
bool is_float(const string &s)
is_float: see the rheostream page for the full documentation
Definition: rheostream.cc:476
rheolef::compose
details::field_expr_v2_nonlinear_node_nary< typename details::function_traits< Function >::functor_type,typename details::field_expr_v2_nonlinear_terminal_wrapper_traits< Exprs >::type... > ::type compose(const Function &f, const Exprs &... exprs)
see the compose page for the full documentation
Definition: compose.h:246
main
int main(int argc, char **argv)
Definition: p_laplacian_fixed_point.cc:30
rheolef.h
rheolef - reference manual
a
Definition: diffusion_isotropic.h:25
eta
Definition: eta.h:25
p
Definition: sphere.icc:25
u
Definition: leveque.h:25
u
Float u(const point &x)
Definition: transmission_error.cc:26
epsilon
Float epsilon
Definition: transmission_error.cc:25